DevTools: Deleting object property in console would just assign it to undefined.

Source/devtools/front_end/sources/WatchExpressionsSidebarPane.js

 /*
  * Copyright (C) IBM Corp. 2009  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 431 matching lines @@
 
     /**
      * @return {boolean}
      */
     renderPromptAsBlock: function()
     {
         return true;
     },
 
     /**
-     * @param {!Event=} event
-     * @return {!Array.<!Element|string>}
+     * @override
+     * @return {{element: !Element, value: (string|undefined)}}
      */
-    elementAndValueToEdit: function(event)
+    elementAndValueToEdit: function()
     {
-        return [this.nameElement, this.property.name.trim()];
+        return { element: this.nameElement, value: this.property.name.trim() };
     },
 
+    /**
+     * @override
+     */
     editingCancelled: function(element, context)
     {
         if (!context.elementToEdit.textContent)
             this.treeOutline.section.updateExpression(this, null);
 
         WebInspector.ObjectPropertyTreeElement.prototype.editingCancelled.call(this, element, context);
     },
 
-    applyExpression: function(expression, updateInterface)
+    /**
+     * @override
+     * @param {string} expression
+     */
+    applyExpression: function(expression)
     {
         expression = expression.trim();
-
-        if (!expression)
-            expression = null;
-
-        this.property.name = expression;
+        this.property.name = expression || null;
         this.treeOutline.section.updateExpression(this, expression);
     },
 
     __proto__: WebInspector.ObjectPropertyTreeElement.prototype
 }
 
 
 /**
  * @constructor
  * @extends {WebInspector.ObjectPropertyTreeElement}
@@ skipping 19 matching lines @@
     },
 
     oncollapse: function()
     {
         WebInspector.ObjectPropertyTreeElement.prototype.oncollapse.call(this);
         delete this.treeOutline.section._expandedProperties[this.propertyPath()];
     },
 
     __proto__: WebInspector.ObjectPropertyTreeElement.prototype
 }